Regulated dc power supply

ABSTRACT

A regulated DC power supply consisting of a voltage regulating circuit which supplies the load with a current just to compensate the variation in the load current and another circuit connected in parallel to said voltage regulating circuit which supplies the remaining and constant portion of the load current, thereby making it possible to reduce the necessary current bearing capacity of the regulating components.

United States Patent [72] Inventors Kojilwata;

Kenjiro Yokoyama, Hitachi-shi, Japan [21 Appl. No. 764,235 [22] FiledOct. 1, 1968 [45] Patented Mar. 23, 1971 [73] Assignee Hitachi, Ltd.

Tokyo, Japan [32] Priority Oct. 2, 1967, Oct. 20, 1967 J p [31] 42/63047and 42/67242 [54] REGULATED DC POWER SUPPLY 3,356,927 12/1967 Barron321/18 3,443,203 5/1969 Krayenbrink... 323/38X 2,092,891 9/1937 Overbeck307/58X 2,495,783 1/1950 Sorensen 307/58 2,872,636 2/1959 Wheatley321/27 3,281,652 10/1966 Perrins 323/19 3,289,069 11/1966 Todd 321/183,375,428 3/1968 Mitchell 323/22(SGR) 3,408,559 10/1968 Bambace et al.323/22(t) 3,447,062 5/1969 Bixby 321/5 FOREIGN PATENTS 718,594 11/1954Great Britain 321/27 Primary ExaminerWilliam M. Shoop, Jr.Att0rneyCraig, Antonelli, Stewart & Hill ABSTRACT: A regulated DC powersupply consisting of a voltage regulating circuit which supplies theload with a current just to compensate the variation in the load currentand another circuit connected in parallel to said voltage regulatingcircuit which supplies the remaining and constant portion of the loadcurrent, thereby making it possible to reduce the necessary currentbearing capacity of the regulating components.

APPS

PATENTED HAR23 l9?! SHEET 2 [IF 2 INVENTORS koa/ llvnrn kmva/Ro Para mwnu E Z m 1 lu N a 1 7w. H a I A ATTORNEYS REGULATEE EEC POWER SUPPLYBACKGROUND OF THE INVENTION This invention relates to a regulated DCpower supply which is especially effective as a DC power supply for alarge current load such as an electronic computer or the electronictelephone exchanger and which is characterized in that a separate supplycircuit is provided in parallel to the ordinary voltage regulatingcircuit. An object of this invention is to obtain a compact andeconomical regulated power supply by making the regulating circuit todeal only with the variable component of the load current.

Another object of this invention is to provide a transistorizedregulated voltage supply of a large current capacity with a regulatingcircuit of a small current capacity, by supplying only one portion ofthe load current through the regulating circuit and regulating theremaining portion of the load current by said one portion.

A conventional regulated DC power supply comprises a variable resistanceelement between the source and the load, and means for detecting theoutput voltage from the regulated power supply per se, resistivity ofsaid variable resistance element being controlled in response to thevoltage detected by said detecting means, and the output voltage beingregulated by the voltage drop across said variable resistance element.

An example of the known regulated power supply is shown in FlG. l. Theoperation of the circuit shown in FIG. B will be described hereunder.The AC current from an AC power source E is rectified through atransformer T, and a diode D charging a capacity C,. The rectifiedcurrent i is fed to a capacity C, connected across the output terminals.Assuming that the terminal voltage of the capacity C is V, and that ofthe capacity C, is the voltage V, must be higher than the voltage V by avalue corresponding to the voltage drop across the variable resistanceelement VR as the current i flows through the element VR.

The voltage V is constantly compared with the reference voltage l by acomparator C which detects any variation in the voltage V andautomatically varies the resistance of the element VR so as to maintainthe voltage V at a fixed value. The voltage regulating circuitrepresented by the variable resistance element VR and the comparator Cis usually constructed as shown in FIG. 2.

in a low voltage power supply, the variable resistance element VR inEEG. l is often comprised of transistors Tr Tr and Tr,,,,..... Tr,,,,,.These transistors are connected all in parallel through the respectiveemitter resistors R R, and El R Variation of the output voltage V isdetected after being divided by the resistors R, and R and is comparedwith the reference voltage V The comparator C provides the transistorswith a bias current depending on the difference between the detectedvoltage and the reference voltage, thereby varying the internalresistances of the transistors "in, Tr and Tr,,,, Tr,,,,,. Thetransistors Tr and Tr serve to amplify the bias currents which aresupplied to the transistors Tr Tr, belonging to the transistor group Tri and the transistors Tr Tr belonging to the transistor group Trrespectively. Accordingly, the emitter to collector resistance of thetransistors Tr Tr, and Tr,,,, Tr is varied depending on the variation ofthe output voltage V so as to suppress said variation of the outputvoltage.

in a low voltage and large capacity power supply used in a largeelectronic computer or electronic telephone exchanger, the number oftransistors connected in parallel to constitute the variable resistanceelement as mentioned above, is otten as many as several hundred. Forexample, in a large electronic computer which takes a DC current of 500to I000 A, the number of said transistors usually reaches the order oftwo hundred, though the number varies more or less depending on thecapacity of the transistors used. Such a power supply unit is inevitablyvery builry, and no attempt to reduce the size of such a unit has yetsucceeded whereas there is a general tendency toward miniaturizedcomputing circuits and memories with the aid of integrated circuits.

According to this invention, the number of transistors which constitutethe variable resistance element as described above can be drasticallyreduced, thus reducing the size of the power unit, by controlling saidvariable resistance unit VR only with a current corresponding to thevaried portion of the output voltage.

BRlEF DESCRIPTlON OF THE DRAWINGS FIGS. l and 2 relate to a conventionalregulated DC power supply as described above;

FIG. 3 is a circuit diagram of an embodiment of the regulated DC powersupply according to this invention;

FIG. 4 is a diagram for explaining the operation characteristics of thecircuit shown in FIG. 3;

FIGS. 5 to 9 show various embodiments of this invention; and

MG. 10 is a diagram showing a waveform related to the operation of thecircuit shown in FIG. 9.

Throughout FIGS. 3 to 10, corresponding components are indicated bysimilar reference marks.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now, referring to FIG. 3, ACcurrent from an AC power source E is rectified by diodes D and D throughtransformers T and T to charge capacitors C and C respectively.

The voltage regulating unit which consists of the variable resistanceelement VR and the comparator C as shown in FIG. l and is constituted asshown in FIG. 2, operates so as to maintain the terminal voltage of thecapacitor C, at a fixed level. Across the capacitor C is connected theDC load to which DC current from the voltage regulating unit AVR and DCcurrent from the diode D and the capacitor C are supplied, the lattercurrent through a resistor R. Thus, the load current i is a sum of thecurrent i, from the regulating unit AVR and the current i from theresistor R. Hereunder, an explanation will be made about the manner inwhich the circuit shown in H6. 3 operates when the load current i variesas shown in H6. 4 as a result of the change in the load.

When the load current 1' assumes a minimum value, the whole current i issupplied through the resistor R, no current being supplied from theregulating unit AVR. if the load current i increases from the value i atan instant I, as shown in H6. 4, the increment i,,=ii i, is suppliedfrom the unit AVR. The resistance of the variable resistance element VRincluded in the regulating unit AVR is adjusted depending on theterminal voltage l of the capacitor C, so as to be kept atV,,,-,,,,,/i,,, V, being the terminal voltage of the capacitor C Now,assuming that the load current 1' decreases at an instant t the currenti from the regulating unit AVR decreases from i u to 1' the resistanceof the unit AVR changing to V,,,-

V /M112. Thus, when the load current i varies from the maximum value ito the minimum value i,,,,,,, the current i, supplied through theregulating unit AVR varies from zero to t so as to maintain the terminalvoltage V of the capacitor C at a constant level, while a constantcurrent i, is supplied to the load through the resistor R.

Further, a circuit as shown in Fit]. 5 also is constructed according tothis invention, in which each pair of two transformers T and T twodiodes D, and D and two capacitors C, and C shown in FlG. 3 is made intoa single unit respectively, thus the current i, and i being suppliedfrom the single rectifier unit.

in the embodiments shown in FIGS. 3 and 5, as described above, thevoltage regulating unit AVR only must have a current capacity sufficientto draw the current i-i corresponding to the current variation in theload current i. That is, in the regulated DC power supply of thisinvention, it is suhicient for the voltage regulating unit to have acurrent capacity of a value corresponding to the expected maximumvariation in the total load current, whereas in the conventionalregulated DC power supply, the voltage regulating circuit must have acurrent capacity for the total load current. Therefore, according tothis invention, a current flowing through the components which comprisethe variable resistance element can be limited to a very small value.

For example, a conventional regulated DC power supply intended for aload which consumes a current of 500 to L000 amperes is required to havea current bearing capacity of l ,000 amperes; while in the power supplyof this invention, the voltage regulating circuit is only required tohave a current capacity of 500 amperes if the variable portion of theload current is 500 amperes. Thus, the number of the transistorsconstituting the variable resistance element of the power supply can bereduced to one-half of that in the conventional device.

in the aforegoing description, the voltage of the AC power source "1d,,was assumed to be constant. If this voltage varies, the collector loss Pof the transistors in the variable resistance element must be taken intoconsideration.

When the emitter to collector voltage of the transistors in the variableresistance element is indicated by V and the total collector current ofsaid transistors I then it will be understood that the product V I mustbe less than the collector loss P Therefore, if the voltage of the ACpower source E increases by AV,,,, the following relation must bemaintained:

Accordingly, the upper limit of the collector current will be lowered.

The above disadvantage is overcome in the embodiment shown in H6. 6.Referring to the FIG, a parallel and reversely connected pair ofthyristors SCR is phase-controlled to adjust the output of the AC powersource E Reference marks T, and T indicate transformers, D, and Ddiodes, CH, and CH choking coils, and C, and C capacitors, respectively.The phase-controlled AC power is rectified through a transformer T,,diodes D, and choking coil Cl-l, to charge a capacitor C,, and at thesame time, said AC power is rectified through a transformer T diodes Dand choking coil CH to charge a capacitor C An automatic pulse positionshifter APPS controls the ignition point of the thyristor-s SCRdepending on the terminal voltage of the capacitor C With this feedbackcontrol, the input voltage V, of the voltage regulating circuit ismaintained at a constant level. It will be understood that the inputvoltage of said automatic pulse position shifter APPS may be taken fromthe terminal of the capacitor C, instead of the capacitor C,. p

in the embodiment shown in FIG. 7, two transformers T, and T in theembodiment shown in FlG. 6 are combined into a single transformer T,.Operation of the device of HO. 7 is similar to that of lFlG. d.

ln the embodiment shown in FIG. 8, the respective pairs of transformers,diodes, choking coils and capacitors in the embodiment shown in FIG. 6are made into respective single components indicated by marks 1",, D,,CH, and C,. in this arrangement too, the feedback circuit including thepulse shifter APPS acts so as to keep the input voltage to theregulating unit AVR constant.

As described above in connection with H68. 6 to 8, in the regulated DCpower supply of this invention which comprises a first circuit forsupplying a DC current i, to the load through the voltage regulatingunit AVR, a second circuit for supplying the remaining portion i, of theload current through the resistor R, said voltage regulating unit AVRbeing operated in response to the output voltage, and a rectifyingcircuit phasecontrolled so as to maintain the input voltage to saidregulat ing unit at a constant level, the required current capacity ofthe variable resistance element in the voltage regulating unit can bedrastically curtailed. Thus, if the variable resistance element consistsof transistors, the transistors to be connected in parallel can bereduced by as many in number, thereby providing a compact and economicalregulated power supply.

Next, another embodiment of this invention will be described referringto H6. 9.

in this embodiment of the invention, the constant component i of theload current i is obtained through a thyristor SCR which isphase-controlled by the automatic pulse position shifter APPS whichgenerates igniting pulses at a phase angle depending on the differencebetween the variable component i, of the load current i and a referencecurrent i,,. That is, if the current i, tends to increase, the ignitingangle of the thyristor SCR is shifted by means of the pulse positionshifter APPS so as to increase the current 1 Reference marking C'indicates a comparator for providing a signal corresponding to thedifference between the current i, and a reference current i,,.

The operation of the circuit shown in FlG. will be described hereunderwith reference to FIG. it).

it is assumed that the load current i decreases by A1 at an instant t,as shown in FIG. iii. The comparator C detects the rise in the outputvoltage V due to the decrease of the load current i and controls thevariable resistance element VR accordingly. Consequently, the current i,tends to drop to i, Ai at the same instant t,. The comparator C detectssaid drop of the current i, and phase-controls the thyristor SCRaccording to the difference between the current i, and the referencecurrent i thereby to decrease the current i, by an amount correspondingto said decrease in the current i In the above operation, the current i,responds to the variation of the load current i at the instant t,without delay, as the comparator C and the variable resistanceelement'VR have been selected so as to have a high speed of response.However, the response of the current i will be delayed at least one-halfcycle period, because the current i, is phase-controlled through thethyristor SCR. Therefore, if the load current i varies by Ar, thecurrent i, immediately varies so as to compensate said variation Ai, andthen the current i varies to take over said variation Ai, thus thecurrent i, is restored to the predetermined constant level. For example,if the load current i decreases at the instant t,, the current i,decreases at the same time, and then the current decreases sensing thedrop in the current i, during the period At, while the current i,returns to the original level.

Also at the instant t if the load current i decreases, the current i,decreases immediately, being followed by the decrease of the current iand the consequent restoration of the current i,. During this regulatingoperation, the relation represented by i i, i is maintained among thecurrents.

Now, assuming that the load current i increases at an instant t thecomparator C detects a drop in the output voltage V, due to the increaseof the load current and acts so as to decrease the resistance of thevariable resistance element VR, thus increasing the current i,. Thecomparator C detects the increase of the current i, over the referencecurrent i and controls the pulse position shifter APPS so as to increasethe conducting angle of the thyristor and therefore to increase thecurrent i Increase of the current i, and i raises the output voltage V,above the reference voltage, which in turn increases the resistance ofthe variable resistance element VB, thus returning the current i, to thenormal level. That is, an increase in the load current i immediatelycauses a corresponding increase in the current i,, being followed by anincrease in the current i, and the consequent restoration of the currenti, to the reference level i Generally speaking, the load current in anelectronic computer or an electronic telephone exchanger varies in stepsas is seen in the current i shown in FlG. W, with a comparably smallvariation in each step. For such a use, the power supply of thisinvention is especially advantageous. That is, the variable resistanceelement VR is only required to have a current capacity equivalent to thesum of the reference current i,, and the momentary rise of the loadcurrent; and if the variation of the load current at an instant, i.e.,one step of the variation is small, the necessary capacity of thevariable resistance element VR becomes considerably small. Therefore,according to this invention, a compact and economical regulated DC powersupply is obtained.

We claim:

1. A regulated DC power supply for supplying a load with DC power,including a voltage regulating circuit having an input and an outputwhich comprises:

means for rectifying an AC input voltage supplied to said input;

variable impedance means for receiving said rectified AC input voltageand for producing a current, the magnitude of which is controlled by thevariation of said variable impedance means, said current being suppliedto said output;

means for controlling the variation of said variable impedance means inresponse to the difference between the voltage at said output and areference voltage;

means for controlling the magnitude of said AC input voltage including aphase-controlled rectifier which is phase controlled in response to thedifference between the current produced by said variable impedance meansand a reference current, to thereby supply said load with a controlledcurrent, a portion of which is supplied by said phase-controlledrectifier; and

a fixed impedance element connected between said phasecontrolledrectifier and said output through which said portion of said controlledcurrent is supplied.

2. A regulated DC power supply for supplying a load with DC powercomprising:

first and second circuits mutually connected in parallel between an ACpower source and a load, wherein said first circuit comprises a meansfor rectifying the voltage produced by said AC power source;

variable impedance means including at least one transistor circuitresponsive to said rectified voltage for supplying a current to saidload, the magnitude of which is varied according to the differencebetween the terminal voltage across the load and a reference voltage;and

said second circuit comprising a phase-controlled rectifier receiving avoltage from said AC power source, responsive to the difference betweenthe output of said variable impedance means and a reference current forcontrolling the magnitude of said AC voltage and for supplying said loadwith a controlled current in addition to the current supplied by saidvariable impedance means.

1. A regulated DC power supply for supplying a load with DC power,including a voltage regulating circuit having an input and an outputwhich comprises: means for rectifying an AC input voltage supplied tosaid input; variable impedance means for receiving said rectified ACinput voltage and for producing a current, the magnitude of which iscontrolled by the variation of said variable impedance means, saidcurrent being supplied to said output; means for controlling thevariation of said variable impedance means in response to the differencebetween the voltage at said output and a reference voltage; means forcontrolling the magnitude of said AC input voltage including aphase-controlled rectifier which is phase controlled in response to thedifference between the current produced by said variable impedance meansand a reference current, to thereby supply said load with a controlledcurrent, a portion of which is supplied by said phase-controlledrectifier; and a fixed impedance element connected between saidphasecontrolled rectifier and said output through which said portion ofsaid controlled current is supplied.
 2. A regulated DC power supply forsupplying a load with DC power comprising: first and second circuitsmutually connected in parallel between an AC power source and a load,wherein said first circuit comprises a means for rectifying the voltageproduced by said AC power source; variable impedance means including atleast one transistor circuit responsive to said rectified voltage forsupplying a current to said load, the magnitude of which is variedaccording to the difference between the terminal voltage across the loadand a reference voltage; and said second circuit comprising aphase-controlled rectifier receiving a voltage from said AC powersource, responsive to the difference between the output of said variableimpedance means and a reference current for controlling the magnitude ofsaid AC voltage and for supplying said load with a controlled current inaddition to the current supplied by said variable impedance means.